Method for hot forming of billets into slugs for an extrusion press

ABSTRACT

The method of processing a ferrous or non-ferrous metal billet to form an extrusion slug is characterized by heating a suitably selected billet to a temperature within the range of 1,600* and 1,850* F. The billet is then loaded into a preheated container of a press. In one embodiment of the invention, a push block is positioned at one end of the container; while the other end of the container is enclosed by a die supported in the press. The billet is then pressed against the die to form at one end of the billet an outside diameter radius or chamfer and a lead-in countersink to an axially extending pilot hole previously drilled in the billet. The billet is then further processed by reheating and expanding the axially extending pilot hole to a desired diameter during which the lead-in countersink provides a reservoir for a vitreous or the like lubricant. The resulting slug is then again reheated to an extrusion temperature and loaded into an extrusion press with the previously formed outside diameter radius adjacent the extrusion press die.

United States Patent 1 [111 3,796,082

Honsinger et al. Mar. 12, 1974 METHOD FOR HOT FORMING 0F BILLETS Primary Examiner-Richard J. Herbst INTO SLUGS FOR AN EXTRUSION PRESS Attorney, Agent, or FirmVincent G. Gioia [75] Inventors: Chester M. Honsinger, Daytona Beach, Fla; William A. Engelke; [57] ABSTRACT :3 B r i i of Troy The method of processing a ferrous or non-ferrous PH usca e metal billet to form an extrusion slug is characterized on by heating a suitably selected billet to a temperature [73] Assignee: Allegheny Ludlum Industries Inc., within the rang of 1,600 and The billet i5 Pittsburgh, Pa. then loaded into a preheated container of a press. In one embodiment of the invention, a push block is po- [22] Ffled' 1972 sitioned at one end of the container; while the other [21] Appl. No.: 294,132 end of the container is enclosed by a die supported in the press. The billet is then pressed against the die to form at one end of the billet an outside diameter rai dius or chamfer and a lead-in countersink to an axially Fieid 264 364 extending pilot hole previously drilled in the billet. r The billet is then further processed by reheating and expanding the axially extending pilot hole to a desired diameter during which the lead-in countersink pro- [56] References C'ted vides a reservoir for a vitreous or the like lubricant.

UNITED STATES PATENTS The resulting slug is then again reheated to an extru- 2,956,337 10/1960 Buffet et al. 72/41 sion temperature and loaded into an extrusion press 2,725,769 12/l955 C a f rd I I 72/253 with the previously formed outside diameter radius ad- 2,7s1,903 2/1957 Buffet et al. 72/256 jacent the extrusion press 3,037,623 6/1962 Rosenkranz H 72/253 9 Claims, 3 Drawing Figures PROVIDE A BILLET I COLD PREPARATION OF BILLET HEAT BILLET T0 I600 F: /850F.

LOAD BILLET INTO CONTAINER 0F PRESS HOT FORM 0. 0. RA 0/05 a cow TEES/NA AT ONE END OF BILLET HEAT BILLET T0 2/50F. -2300F.

EXPAND 1.0. 0E

BILLET REHEATEILLET SOLID BILLET 2/50 F Z300"E WITHOUT PILOT/IDLE EXTRUDE IN PRESS l PATENTEUMAR 12 I874 SHEET 1 BF 2 FIG. I.

PROV/0E BILLET FIG. 3.

COLO PREPARATION OF BILLET HEAT BILLET TO 2/50F. -2300F.

SOL/D BILLET WITHOUT PILOT/ OLE EXPAND [.0. OF

BILLET REHEAT BILLET 2/50" F 2300"F EXTBUDE IN PRESS METHOD FOR HOT FORMING OF BILLETS INTO SLUGS FOR AN EXTRUSION PRESS BACKGROUND OF THE INVENTION The typical extrusion plant for ferrous metals employs bar stock in the form of suitably prepared rounds or, in other cases, round cornered squares are used. The stock is cut into billets having a length selected for the extrusion operation. When stainless steel tubes are to be produced, the surface of the billet is machined and a small pilot hole is drilled along the axis of the billet. A comer radius and a lead-in countersink to the axially aligned hole are also machined. The billets are then heated to a piercing temperature and placed in a vertical piercing press for enlarging the pilot hole to form the extrusion slug. In certain cases, this piercing operation may be performed by the extrusion press. The slug is then cleaned and reheated to an extrusion temperature and placed in the container of an extrusion press for the formation of the tubular article.

The actual preparation of the slug includes machining operations that contribute materially to the overall expense of the extrusion plant operations. These expenses may be highlighted in terms of the time, labor and actual loss of billet metal along with ancillary operational expenses, all of which reach substantial proportions in terms of annual operating costs.

SUMMARY OF THE INVENTION It is an overall object of the present invention to enhance extrusion plant operations by improving the processing of slugs for an extrusion press while reducing the time and expense for producing such slugs.

Another object of the present invention is to provide a method of preparing a billet form a slug for an extrusion press wherein the billet undergoes a forming operation at an elevated temperature to provide, at one end of the billet, an entry countersink for a pilot hole drilled along the axis of the billet. The countersink provides a lead-in entry for a piercing tool and a reservoir for lubricant during hot expanding operations to enlarge the pilot hole to a desired bore in a slug for extrusion. The present invention further provides that the same end of the billet is hot formed with a radius at the outsidediameter to facilitate the actual extruding process.

It is a further object of the present invention, in the above-described process, to heat the billet to a temperature of at least 1,600 F to thereby reduce the resistance of the ferrous metal to deformation. In its preferred form, the present invention provides that the billet is heated to a temperature selected within a range of l,600 and l,850 F.

An additional object of the present invention is to carry out the hot forming process in a vertical press having a preheated billet container into which there is received the billet. A push block at one end of the container presses the billet against a die at the other end of the container to form the desired shape at the end of the billet.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a flow diagram of the hot forming process for billets according to the present invention;

FIG. 2 illustrates one form of a hot forming die assembly for a vertical press; and

FIG. 3 illustrates a second embodiment of the hot forming die similar to that illustrated in FIG. 2.

The initial step in the process according to the present invention, as illustrated in F IG. 1, is to provide a billet having a desired length and diameter from ferrous metal stock such as stainless steel rounds when extruding stainless steel tubing, non-ferrous alloys such as copper and titanium and refractory alloys such as molybdenum and columbium. The billet in the next step undergoes certain preparations, which include machining the cylindrical surface of the billet and the drilling of a small pilot hole along the axis of the billet. These preparations are concluded with a cleaning process to remove grease, oil and other foreign matter frornthe billet. During these operations, the billet remains substantially at an ambient temperature.

The billet is then heated to a temperature of l,600 F, preferably within a temperature range of l,600-l ,850 F. The actual temperature of the heated billet is selected according to the metallurgical composition of the billet in order to reduce the resistance to deformation, and thereby enhance the hot forming process. For stainless steel billets, it is preferred to employ an induction heating furnace since this heating method minimizes the formation of scale. The billet is then loaded into the container of a vertical press for the step of, as indicated in FIG. 1, forming an outside diameter radius and countersink. One form of apparatus provided for this forming operation is illustrated in FIG. 2 and includes a holder 10 positioned within a vertical press which includes a bottom platen 1 l. The holder 10 has a cylindrical opening for receiving a tubularshaped container 12. The container 12 has a reduced diameter at each end defining a recess 13 for receiving a locking or retainer ring 14.

The inside surface of the container 12 is tapered for receiving the similarly-tapered surface formed on a liner 15. The liner has a bore slightly greater in diameter than the diameter of the billet to be loaded therein. A recess 17 is formed in the lower end surface, as one views FIG. 2, of the liner for supporting a reduced diameter collar 18 formed on a die 19. The die 19 is actu ally formed in two pieces consisting of a radius forming backup ring 21 and a countersink punch 22. The backup ring has an inside diameter substantially equal to the bore in the liner to thereby provide a continuous cylindrical surface which terminates in the die with an end radius R. A series of circumferentially arranged vent holes 23 exhaust to the atmosphere entrapped airv between the billet and the die during the hot forming process. The punch member 22 isslideably received within a circular opening 25 formed in the backup ring 21. The working surface of the punch 22 comprises a spherical projection 26 for initial penetration into the end of the billet. The projection 26 extends from 'a tapered surface 27 which def nes a countersink formation member.

After preheating the liner 15 and to a limited extent, the holder 12, a heated billet is loaded into the container wherein the billet comes to rest on the projection 26. A push block 29 is positioned on the opposite end of the billet. A press ram 30 is then brought into engagement with the push block and a predetermined force is established between the block 29 and the platen llto cause the die 19 to penetrate the end surface of the billet whereby a radius R is formed on the outside diameter of the billet and a hollowed out countersunk area is centrally arranged in the end of the bi]- let. It is to be appreciated that, in a given instance, solid billets are hot formed with only an outside diameter radius. In this event, according the present invention, the

punch 22 is replaced with a circular block to eliminate the projection 26 and tapered surface 27.

A lubricant is applied to the die in order to protect the working surface of the die. The following table represents test results on six billets which were hot formed using the die apparatus illustrated in FIG. 2:

TABLE I Forming OD Radius ID counter- Billet Temp. Force (percent of sink No. (F) (Tons) 3'4" R) (Depth in.) l 1800 500 75 lli (Full) 2 1800 275 55 1% 3 1800 200 50 1 /16 4 I600 250 4O 1% 5 I800 500 65 l 7/16 6 1600 250 (Slight Chamfer) 1% In this test, heated billets were transferred manually to the container 12 and inserted into the liner 15. Quickness in the transfer was emphasized and the liner was preheated to minimize temperature loss. Separation of the billets from the die was accomplished with little difficulty. The die was designed to produce a threequarter inch outside diameter lead-in radius on the billet and a 1% inch deep countersink. The test results given in FIG. 1 confirmed that the hot forming process according to the present invention is a feasible and sound process.

FIG. 3 illustrates a modified die construction for the hot forming process according to the present invention. The die 31 is constructed as a one-piece die member. The chamfered surface 32, at the upper end of the die, is brought into a mating relation with a similarly-shaped surface formed in the liner 33 located within the container 12. The working surface of the die includes a radius R for the formation of a radius on the outside diameter at the end of a billet. A centrally arranged projection 34, for the formation of a hollowed out countersink in the end of the billet, is characterized by a spherical surface 35 at its projected end which terminates into an enlarged base 36 formed as a depressed radius R;,, an extended radius R, followed by a depressed radius R By designing the countersink die from a series of radii R R and R the countersink formed in the billet has an increased hollowed out surface area thus not only providing greater capacity as a reservoir for the vitreous lubricant but also facilitates the initial penetration into the billet by a mandrel to expand the pilot hole to a desired diameter. Table II contains the details of the hot forming operation on seven billets using the die design shown in FIG. 3. I

TABLE II Forming OD Radius ID Counter- Billet Temp. Force Percent sink No. (F) (Tons) 1" R (Depth in.) 1 1800 850 4 75 1% 2 1600 850 80 1% 3 1800 850 35 1% 4 1800 850 35 1:4 5 1600 850 35 1 /16 6 1850 755 100 1% 7 1600 755 20 1% After hot forming an outside diameter radius and, when desired, a countersink at one end of the billet, the method according to the present invention provides for reheating the billet to a temperature of l,800 F or greater, preferably within the range of 2, l 502,300 F. The billet is then loaded into the container of a press with the countersink arranged for entry of a mandrel to expand the pilot hole in the billet to a'desired bore thus forming a slug for an extrusion press. This expanding operation may be carried out according to the method described in US. Pat. No. 2,956,337. These slugs are reheated to a temperature of 2,150-2,300 F and then loaded into an extrusion press to form the tubularshaped article as desired. In a given plant operation, the extrusion press may be equipped with a mandrel to expand the inside diameter of the billets to be followed immediately by the actual extrusion process. It will be appreciated by those skilled in the art that when a solid slug is desired for use in an extrusion press, the previously-described pilot hole and expanding operation thereto are eliminated.

The billets which were hot formed according to Table II above, were reheated to a temperature within the range of 2,2002,300 F. The billets were then loaded into the container of a press and their pilot holes expanded to a diameter of 4.375 inches. A smooth expanding operation was obtained. The countersinks were found to provide an adequate reservoir for a lubricant which can be utilized in the form of a powder or fiber. It is preferred to select such a lubricant that melts partly or wholly at the working temperature of the billet while remaining viscous at that temperature'The lubricant selected may take the form of glass, salt or slag. Glass powder and fiberglass are two preferred forms of a vitreous lubricant.

The resulting extrusion press slugs were produced at a substantial reduction in cost while possessing a comparable quality to blanks produced by cold machining operations. The slugs produced from the billets in Table 11 were extruded into tube hollows having a nominal 4.50 inch OD by 0.220 inch wall thickness. The inspection results of the tube hollows are given in Table 111.

TABLE III Surface Tube Front (Inch) Back (Inch) Condition No. OD Wall OD Wall 0D ID m (A g) 1 4.497 .251 4.488 .25- Fair Light Impression 2 4.475 .261 4.490 .248 Fair Good 3 4.476 .248 4.485 .239 Fair Good 4 4.487 .254 4.505 .247 Fair Good 5 4.475 .253 4.487 ,2A3 Fair Good 6 4.492 .257 I504 .247 Fair Good 7 4.480 .249 4.507 .246 Fair Good Although the invention has been shown in connection with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

We claim 1. A method of hot forming a billet to produce a slug for the production of tubes orthelike by a hot extrusion process, said method comprising the steps of:

providing a metal billet characterized by a desired length and outside diameter for the production'of said slug, said billet having an axially extending pilot hole with a diameter less than a desired bore in said slug;

heating said billet to a temperature of at least 1600F for reducing the yield point of the metal;

forming a countersink at one end of said billet while in the heated state to define a lead-in entry countersink for said pilot hole;

reheating said billet to a temperature of at least l,800 F; I

loading said billet into the container of a press;

applying a lubricant within'said countersink; and

enlarging said pilot hole to a predetermined diameter selected for a slug incident to forming a tubular article by a hot extrusion process. t,

2. The method of claim 1 wherein said step of forming a countersink at one end of said billet is further defined to include forming a radius at the outside diameter of said billet.

3. The method of claim 2 including the step of applying a lubricant to a die prior to said step of forming a countersink at one end of said billet to facilitate removal of said die from said countersink.

4. The method of claim 3 wherein said billet is heated to a temperature within the range of l,600-1,850 F prior to said step of forming a countersink at one end of said billet.

5. A method of hot forming a billet to provide a slug for an extrusion press comprising the steps of:

providing a metal billet characterized by having a desired length and outside diameter for the production of said slug;

heating said billet to a temperature of at least 1600F for reducing the yield point of the metal;

loading said billet into a container of a press;

closing one end of said container with a die;

forming a radius on the outside diameter of said billet by applying a deformation pressure between said billet and said die; and

loading said billet in the container of an extrusion press such that said radius is located adjacent the extrusion press die.

6. The method according to claim 5 wherein said step of providing a metal billet is further characterized by providing in said billet an axially extending pilot hole with a diameter less than a desired bore in said slug; and said step of forming a radius is further defined to include forming an entry countersink for said pilot hole.

7. The method of claim 6 including the step of applying a lubricant to said die prior to said step of loading said billet into a container of a press.

8. The method of claim 7 including the further step of preheating said container prior to loading said billet therein.

9. The method of claim 8 wherein after said step of forming a radius, the method further includes the steps of reheating said billet to a temperature of at least 1,850 F; applying a lubricant to said entry countersink; Y

into a predetermined shape. 

1. A method of hot forming a billet to produce a slug for the production of tubes or the like by a hot extrusion process, said method comprising the steps of: providing a metal billet characterized by a desired length and outside diameter for the production of said slug, said billet having an axially extending pilot hole with a diameter less than a desired bore in said slug; heating said billet to a temperature of at least 1600*F for reducing the yield point of the metal; forming a countersink at one end of said billet while in the heated state to define a lead-in entry countersink for said pilot hole; reheating said billet to a temperature of at least 1,800* F; loading said billet into the container of a press; applying a lubricant within said countersink; and enlarging said pilot hole to a predetermined diameter selected for a slug incident to forming a tubular article by a hot extrusion process.
 2. The method of claim 1 wherein said step of forming a countersink at one end of said billet is further defined to include forming a radius at the outside diameter of said billet.
 3. The method of claim 2 including the step of applying a lubricant to a die prior to said step of forming a countersink at one end of said billet to facilitate removal of said die from said countersink.
 4. The method of claim 3 wherein said billet is heated to a temperature within the range of 1,600*-1,850* F prior to said step of forming a countersink at one end of said billet.
 5. A method of hot forming a billet to provide a slug for an extrusion press comprising the steps of: providing a metal billet characterized by having a desired length and outside diameter for the production of said slug; heating said billet to a temperature of at least 1600* F for reducing the yield point of the metal; loading said billet into a container of a press; closing one end of said container with a die; forming a radius on the outside diameter of said billet by applying a deformation pressure between said billet and said die; and loading said billet in the container of an extrusion press such that said radius is located adjacent the extrusion press die.
 6. The method according to claim 5 wherein said step of providing a metal billet is further characterized by providing in said billet an axially extending pilot hole with a diameter less than a desired bore in said slug; and said step of forming a radius is further defined to include forming an entry countersink for said pilot hole.
 7. The method of claim 6 including the step of applying a lubricant to said die prior to said step of loading said billet into a container of a press.
 8. The method of claim 7 including the further step of preheating said container prior to loading said billet therein.
 9. The method of claim 8 wherein after said step of forming a radius, the method further includes the steps of reheating said billet to a temperature of at least 1,850* F; applying a lubricant to said entry countersink; and enlarging said pilot hole with a mandrel to a desired diameter for subsequent extrusion of the billet into a predetermined shape. 